Electric fuse



Nov. l2, 1929. H. T..BUssMANN 1,735,572

' ELECTRIC FUSE Filed March 20. 1922 Patented Nov. 12, 1929 PATENT OFFICE f HENRY T. BUssMANN, or sr. Lo'UIs, MISSOURI ELECTRIC FUSE y i pplicafin mea kann 2o, 1922. Yserial No. 545322./

My invention relates to electric fuses and refers particularly to that type of fuse known as the -renewable ferrule-contact type, and the object of my invention is t provide a fuse that is simple to renew, having a minimum number of parts and yet, safe in operation and capable of being renewed indefinitely.

These advantages of my invention will be more readily understood by reference to the accompanying drawings which show a preferred embodiment of my invention. In describing the device shown in the drawings hereto attached and described in the specification, Ido not limit my invention to the precise form, shape or construction of the fuse shown or to the several parts thereof, asI am aware of the fact that various alterations can be made without changing the scope of my invention.

Fig. 1 is a view of my fuse showing a longitudinal section thereof.

Fig. 2 is a perspective view of the parts thereof.

Fig. 3 shows the end of the fuse not shown in Fig. 2. l

In the drawings, 6 is a casing having threads 7 at each end. 8 and 9 are members attached to the casing to hold the ferrules 10, 10 by means of threads 11. As shown in Fig. 1, these members are threaded on and overlap the casing and the root diameter of their outer threads is less than the diameter of the casing. This construction gives the fuse the required holding strength against the internal pressure caused by the blowing of the link. By using threads I am enabled to leave the thickness of the wall of the fibre tube and the thickness of the metal of substantial proportion, whereas this would be impossible with any other method of attachment. It is, of course, well known that the attaching of caps or ferrules such as shown at 10 directly to the fibre tube has a great many disadvantages. Fibre will swell when subjected to even a small amount of dampness, and when this occurs it can be readily seen that any cap attached directly to the fibre would be gripped so tightly that it could not be removed and replaced. For this reason, the members 8 and 9 are provided.

The member 8 isy provided with a large opening 12 to permit the removal of parts of the link remaining after the fuse is blown Y and to permit cleaning of the fuse. This opening is made square and the link set along one of the sides of this square opening and Iis held in position at that point by the slot 13 and washer 14.- In this manner turning and twisting of the link is prevented. It is, of course, apparent that any twisting of the link would result in injury thereto, and such injury I avoid by the method described. The washer 14 closes the balance of the opening 12 not occupied by the link. By making this opening square and holding the link to one of the sides of this square opening the link is held away from the center of the casing and then when it is bent back on the washer, a greater contact area is presented, than would be the. case if the link were in the center of the casing.

The member 9 has an opening 15 only slightly larger than the link and the seat for the link is integral with the member. This does away with the need for a separate washer. The slot 15 being located near the wall of the casing instead of the center of the casing makes it possible to have the greatest possible contact surface for the link when it is bent back on the member. The link 16 may be of any suitable type.

The ferrules or caps 10, 10 are provided with the projection 17 surrounded by an open space as shown at 18. When a fuse is blown a metallic deposit is formed on the inner surface of the closure. This results in injury to the contact and causes the cap to stick to the members. By providing the cap with a limited contact area in the form of the projection 17 which is approximately the 90 width of the link, I find that much better contact can be obtained. The large area of metallic-surface 18 also assists very greatly in quickly condensing the vapors or gases caused by the blowing of the fuse because 95 these metal end pieces are very considerably cooler than such gases.

I prefer to make the washer 14 circular and then provide the slot 13 because when the link is bent back down on this washer, it is positioned by the link and the user is not subjected to the inconvenience of having the washer drop to the floor. By making this washer flat without any projection it can be readily cleaned and there is no possibility of the washer being improperly seated as would be the case if this washer had any vcan be experienced in renewing the fuse and a long life of the fuse can be expected.

I claim as my invention: l. In a ferrule contact renewable fuse adapted to contain a link having at contact surfaces, a casing threaded at'the end, a ferrule holding member overlapping the end of the casing and a ferrule substantially enveloping the ferrule holding member; the ferrule holding member having interior threads for engagement with casing threads and exterior threads for engaging threads in the ferrule, the exterior threads having a root diameter not greater than the outside diameter of the casing, the exterior and interior threads being longitudinally offset, relative to each other, so as to provide a side Wall of substantially uniform thickness, on the holding member.

2. In a renewable fuse adapted to contain a fuse link having Hat contact surfaces, ferrules at each end of the fuse, a casing threaded at both ends, ferrule holding members overlapping the ends of the casing and substantially enveloped by said errules; said ferrule holding members u aving interior threads for engagement with casing threads and exterior threads for engagin threads in the ferrules, the exterior threa s having a root diameter not greater than the outside diameter of the casing, one of the ferrule holdingmembers having an eccentrically located opening for the link, the other errule holding member having a relatively large opening to permit cleaning of the casing, and a closure for such opening acting as a seat for the link. y

3. -In a ferrule contact fuse, a link having flat contact surfaces, a casing threaded at the end, a cap holding member overlapping the ends of the casing anda cap substantially enveloping the cap holding member; said cap holding .member being threaded interiorly and exteriorly in such a way that the exterior threads have a root diameter not greater than the outside diameter of the casing, the member having a substantially square opening therethrough into the casing of substantial size so as to permit cleaning of the caslink having fiat contactsurfaces, ferrules at each end of the fuse, a casin threaded at both ends, ferrule holding mem ers overlapping the ends of the casing and having interior threads for engagement with casing threads and exterior threads for engaging threads in the ferrules, one of the ferrule holding members acting as a seat for the link and substantially closing the end of the casing except for an opening to permit the link to be passed therethrough, said opening being eccentric to the axis of the casing; the other member having an opening of substantial size to permit cleaning of the casing, said opening having a plurality of straight sides each at least as wide as the link and a washer acting as a seat for the link and substantially closing the opening in the member except for an opening to permit the link to be passed therethrough, said opening in the washer being eccentric to the axis of the casing.

5, In a renewable fuse adapted to contain a fuse link having flat contact surfaces, ferrules at each end of the fuse, a casing threaded at both ends, ferrule holding members overlapping the ends of the casing and substantially enveloped by said ferrules; said errule holding members having interior threads for engagement with casing threads and exterior threads for engaging threads in the ferrules, the exterior threads of said members having a root diameter not greater than the outside diameter of the casing, one of the ierrule holding members havinor an eccentrically located opening for the Iink, said ferrule holding member acting as a seat for the end of the link, whereby the link may be clamped between the ferrule and the ferrule holding member.

HENRY T. BUSSMANN.

ing, a washer closing suchpopemng and heldA in position by the cap.

4. In an enclosed renewable fuse, a fuse 

